The present invention relates to transient suppression devices, and in particular, to transient suppression snubber devices for power supply circuits. In particular, the present invention relates to an active snubber device for power modules, for example, power modules having power switching transistors such as insulated gate bipolar (IGBT) power transistors.
In the past, snubbers for power modules have included passive devices using large components to dissipate energy, often continuously. For example, in power transistor switching circuits, passive components comprising resistors, capacitors and diodes have been used to snub out transient spikes created from switching inductive loads or due to the internal inductive energy of the power switching devices themselves.
FIG. 1 shows an example of such a prior art snubber. As shown in FIG. 1, an insulated gate bipolar transistor (IGBT) 1 is provided with a control signal at its gate which controls the switching of a load coupled into the emitter collector circuit. If the load is inductive or due to the stray inductance, when the IGBT switches, voltage spikes are produced. A snubber is provided in the circuit of FIG. 1 comprising a capacitor 2, diode 4 and resistor 6. The snubber circuit, as well known in the art, absorbs transients and other spikes. However, although performing this function very well, the passive snubber circuit typically comprises very large capacitances and resistances which present problems with respect to cost, space saving designs and miniaturization.